There are ever increasing applications which require transmission of high rate data, such as high definition video, over both wired and wireless channels. The effective channel rate is a function of the channel condition (noise), distance and the power/sensitivity capabilities of both the transmitter and receiver. A shortcoming in one must be made up by a strength in another. For example, based upon its sensitivity, a receiver must be close enough to the transmitter to “hear” it correctly. If the channel condition is noisy, however, then that maximum distance may be reduced. The transmitter's power can also be increased to overcome channel limitations, distance and/or receiver sensitivity. Coding schemes may reduce (or even increase) the signal-to-noise ratio (SNR) for a particular signal. As the number of bits per symbol increases, so do the SNR requirements. Conversely, lower bits per symbol can typically tolerate more signal noise. In general, lower channel rates tend to have better noise immunity and/or range.
In certain wired communication links (e.g., Ethernet) and most wireless links, no separate data clock is transmitted from the transmitter-side to the receiver-side and, accordingly, various techniques have been employed on the receiver-side to recover the data clock from the transmitted signal. For example, the receiver-side may generate a clock based on a reference frequency, and then phase-align this clock to the transitions in the data stream with a phase-locked loop (PLL). This process is commonly known as “clock and data recovery” (CDR). In order for CDR to function properly, a data stream should transition frequently enough to correct for any drift in the PLL's oscillator. Thus, it is necessary to employ an encoding scheme that ensures frequent transitions.
In the context of communications with varying channel rates, CDR requires an infinitely greater amount of processing since the receiver-side will have essentially no information regarding the incoming data. Thus, there is still an unsatisfied need for a system and method for transmitting data using quantized channel rates in order to simplify the process of performing CDR.